Oxygen scavenging polymers

ABSTRACT

A polymer with a backbone having at least one structural unit represented by formula (I): 
     
       
         
         
             
             
         
       
     
     Wherein R 1 , R 2 , R 3 , R 4 , and R 5  independently denote one of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted alkenyl group, and n preferably denotes an integer from 1 to 10.

This application claims the benefit of U.S. Provisional Application Ser.No. 60/659,617, filed Mar. 8, 2005, and 60/669,571, filed Apr. 8, 2005,the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This invention relates to an oxygen scavenging polymer. The polymer maybe applied to a package, or made into packaging, wrapping and storagearticles to preserve the freshness of, for example, foods and beverages.

BACKGROUND

Plastic materials can be used in a wide variety of packaging, wrapping,and storage articles. Plastic materials traditionally have not had goodbarrier properties to gases (particularly oxygen). Plastics havegenerally functioned poorly at excluding oxygen passage compared withother available materials, such as glass or metal.

However, despite this shortcoming, some plastic materials have becomewidely used for some packaging applications. For example, polyethyleneterephthalate (PET) has become widely used for soft drink bottles, waterbottles, and the like. However, the barrier properties of PET havelimited its use for other applications in which the package contents aremore susceptible to degradation from exposure to oxygen. For example,glass still predominates in juice and beer bottling.

To reduce gas transmission of a plastic packaging material, a passivebarrier may be used to hinder the passage of a gas, e.g. oxygen. Forexample, in a multi-layer bottle, the inner and outer layers may be madeof PET, while the center layer is a different material with passivebarrier properties such as, for example, ethylene vinyl alcohol (EVA).However, layers of dissimilar materials often do not adhere well to oneanother, and an adhesive between the layers may be required to preventdelamination. The clarity of the packaging material may be reduced whena passive barrier material is used, and the multi-layered material maybe more difficult to recycle.

An active oxygen scavenging system, which reduces or depletes the oxygenin an environment, may be used to overcome at least some of thelimitations of a passive barrier system. An active oxygen scavenger,such as a polyamide or a polyolefin, may be incorporated into thebackbone of a base polymer material making up the walls of the packageto form an oxygen scavenging polymer. The oxygen scavenging polymer maybe used in a blend with other polymers, or as an oxygen absorbing layerin a multi-layer container.

However, since the oxidation occurs in the backbone of the polymer, theproperties of the oxygen scavenging polymer may change compared to theunmodified base polymer. As a result of the oxidation, the polymer mayeven begin to degrade over time. Polyamide systems often yellow due tooxidation, and this oxidation may occur during injection molding of theoriginal articles, during storage, use, or during recycling.

SUMMARY

In formulating an oxygen absorbing polymer, the challenge for thepackage designer is to balance barrier properties, clarity,recyclability, and cost, while preserving as many of the beneficialproperties of the unmodified base polymer as possible.

In one aspect, the invention is an oxygen scavenging polymer including abase polymer suitable for use in packaging applications, such as forexample, a polyester, a polyurethane, a polyepoxide, or a polyamide,which has attached to its backbone an unsaturated side chain with one ormore carbon-carbon double bonds. The one or more carbon-carbon doublebonds in the side chain do not involve the first carbon atom of the sidechain, which as defined herein is the carbon atom located adjacent tothe polymer backbone.

In one embodiment, the invention is an oxygen scavenging polymer with abackbone having at least one structural unit represented by formula (I):

Wherein

R₁, R₂, R₃, R₄, and R₅ independently denote one of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedcycloalkyl group, or a substituted or unsubstituted alkenyl group;

R₁, R₂, R₃, R₄, and R₅ preferably each have less than 20 carbon atoms;and

n preferably denotes an integer from 1 to 10.

In another aspect, the invention is an oxygen scavenging polymercomposition including the oxygen scavenging polymer and an oxidationcatalyst.

In yet another aspect, the invention is a solution or a dispersionincluding the oxygen scavenging polymer and/or composition and asuitable solvent. The solution or dispersion may be applied, forexample, as a coating for packaging articles.

In yet another aspect, the invention is a packaging material includingthe oxygen scavenging polymer and/or composition. The packaging materialmay include the oxygen scavenging polymer and/or composition as a blendwith other polymers in a single layer package such as a bottle or afilm. Or, the oxygen scavenging polymer and/or composition may be usedalone or as a blend with other polymers in one or more layers in amulti-layered package such as a bottle or a film.

In yet another aspect, the invention is a method for making the oxygenscavenging polymer including reacting one of a polymer precursor or apolymer with a succinic anhydride derivative and a polymerizationcatalyst. A suitable succinic anhydride derivative includes the reactionproduct of maleic anhydride and a substituted alkene. Preferredsubstituents for the substituted alkene include saturated or unsaturatedhydrocarbon chains, which may be substituted or unsubstituted, andsubstituted or unsubstituted phenyl groups.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription, and from the claims.

DETAILED DESCRIPTION

In one aspect, the invention is an oxygen scavenging polymer. As usedherein, the term “oxygen scavenging” means absorbing, consuming, orreducing the amount of oxygen from a given environment. The oxygenscavenging polymer includes a base polymer suitable for packagingapplications that is modified with an unsaturated side chain attached toits backbone. Preferably, the unsaturated side chain has one or morecarbon-carbon double bonds, and the side chain enhances the oxygenscavenging capacity of the polymer compared to its unmodified base form.The one or more carbon-carbon double bonds in the side chain preferablydo not involve the first carbon atom of the side chain located adjacentto the polymer backbone. Preferably, the one or more carbon-carbondouble bonds present in the side chain include a single carbon-carbondouble bond, and, assuming the carbon atom adjacent to the backbone isreferred to as carbon 1 of the side chain, this single double bond ispreferably located between the second and third carbon atoms in the sidechain. As used herein, the term “carbon-carbon double bond” means adouble bond between two carbon atoms, but excludes the double bonds ofan aromatic ring.

The backbone of the oxygen absorbing polymer may have differentconfigurations depending upon the type of monomer block used in thepolymerization of the base polymer material for the packaging product.Different monomer blocks may be chosen depending on the intendedapplication, including the desired properties of the final product, theexpected use of the polymer composition, the other materials with whichthe polymer composition will be mixed or come into contact, or the typeof polymer desired. Depending upon the precursors chosen, the polymerbackbone may be, for example, a polyester, a polyurethane, apolyepoxide, or a polyamide. A polyester backbone is particularlypreferred.

In one embodiment, the oxygen absorbing polymer backbone has at leastone structural unit represented by formula (I):

In formula I, R₁ denotes one of a hydrogen atom, a substituted orunsubstituted alkyl group, a substituted or unsubstituted cycloalkylgroup, or a substituted or unsubstituted alkenyl group. R₁ preferablyhas less than 20 carbon atoms, more preferably less than 10 carbonatoms. Most preferably, R₁ is H.

R₂ denotes one of a hydrogen atom, a substituted or unsubstituted alkylgroup, a substituted or unsubstituted cycloalkyl group, or a substitutedor unsubstituted alkenyl group. R₂ preferably has less than 20 carbonatoms, more preferably less than 10 carbon atoms. Even more preferably,R₂ is a substituted or unsubstituted alkyl group, which may be linear orbranched, that has 1 to 10 carbon atoms. Most preferably, R₂ is a linearalkyl group with 1 to 10 carbon atoms, and a in a particularly preferredembodiment R₂ has 5 carbon atoms.

R₃ denotes one of a hydrogen atom, a substituted or unsubstituted alkylgroup, a substituted or unsubstituted cycloalkyl group, or a substitutedor unsubstituted alkenyl group. R₃ preferably has less than 20 carbonatoms, more preferably less than 10 carbon atoms, and most preferably R₃is H.

R₄ denotes one of a hydrogen atom, a substituted or unsubstituted alkylgroup, a substituted or unsubstituted cycloalkyl group, or a substitutedor unsubstituted alkenyl group. R₄ preferably has less than 20 carbonatoms, more preferably less than 10 carbon atoms, and most preferablywill denote a hydrogen atom.

R₅ denotes one of a hydrogen atom, a substituted or unsubstituted alkylgroup, a substituted or unsubstituted cycloalkyl group, or a substitutedor unsubstituted alkenyl group. R₅ preferably has less than 20 carbonatoms, more preferably less than 10 carbon atoms, and most preferablywill denote a hydrogen atom.

In formula (I), n preferably denotes an integer from 1 to 10. Morepreferably, n will be an integer less than 5, and more preferably n=1.

Further, in formula (I), R₂ and R₃ may be interchanged as a result ofstereochemistry about the double bond.

In one particularly preferred embodiment, R₁, R₃, R₄ and R₅ denote ahydrogen atom, and R₂ is a linear substituted or unsubstituted alkylgroup with 1 to 10 carbon atoms, more preferably 5 carbon atoms, andn=1.

Although not intending to be bound by any theory, it is believed thatthe active oxygen scavenging ability of the oxygen scavenging polymer isbased on the one or more carbon-carbon double bonds in the side chain ofthe polymer, which are exposed and available for oxidation.

Since the double bonds on the side chains in the oxygen scavengingpolymer are in large part responsible for its oxygen scavengingproperties, the number of unsaturated side chains present in the polymeris an important factor in determining its oxygen scavenging capacity. Asufficient number of side chains should be present for the polymerand/or composition to perform adequately, and for a suitable length oftime.

However, while adding more side chains increases the oxygen scavengingability of the oxygen scavenging polymer, increasing the number of sidechains also begins to alter the quality and characteristics of thepolymer compared to its unmodified base form. For example, adding toomany side chain monomers may cause the resulting oxygen scavengingpolymer to have a lower glass transition temperature (T_(g)), meltingpoint, or physical properties compared to an unmodified base polymerwithout the side chains. For example, in some embodiments it has beenfound that when the side chain monomers present in the oxygen scavengingpolymer approach about 30% by weight, the polymer may start to becomemore rubbery compared to the unmodified base polymer. In addition, forexample, if the side chains are too large, the oxygen scavenging polymermay begin to plasticize and/or agglomerate. In preferred embodiments,the side chains constitute between 1 and 30 weight percent of the oxygenscavenging polymer. More preferably, the side chains constitute between2 and 25 weight percent of the oxygen scavenging polymer, mostpreferably between 5 and 24, and optimally the side chains constitutebetween 10 and 20 weight percent of the oxygen scavenging polymer.

As the properties of the oxygen scavenging polymer can change based onthe percentage and size of the side chains present, it is important tomonitor the physical properties of the polymer. For example, increasingthe amount of branching in the backbone of the oxygen scavengingpolymer, or increasing the number and/or the size of side chains presentin the oxygen absorbing polymer beyond a certain level may result inchanges in viscosity. Many manufacturing processes are optimized andconstructed to operate within certain viscosity and temperature ranges,and changing these physical properties can increase processing costs.Thus, the side chains are preferably present in an amount sufficientsuch that the viscosity remains in the desired target range.

For example, when used with other polymers, such as in a blend, theviscosity of the oxygen absorbing polymer preferably should be similarto that of the other polymer(s) in the blend. Or, if a multi-layerpackaging article is to be produced, the size and number of side chainsmay make the oxygen scavenging polymer increasingly different from theother layers. This can decrease the clarity of the final product, andmay cause the layers of the resulting article to separate from oneanother.

An optional oxidation catalyst is preferably present with the oxygenscavenging polymer to form an oxygen scavenging polymer composition. Theoxidation catalyst enhances the oxygen scavenging properties of theoxygen scavenging polymer by catalyzing an oxygen scavenging reactionwith the side chains attached to the polymer backbone. While not wishingto be bound by any theory, the oxidation catalyst is believed to assistin activating the double bond(s) of the side chain(s) of the oxygenscavenging polymer to facilitate a reaction with oxygen.

If desired, the oxygen scavenging polymer composition may be dissolvedin a suitable solvent to form a coating solution, or may be blended withwater and/or a suitable solvent to form a coating dispersion. Thecoating solution or dispersion may be applied using known methods, e.g.spraying, onto a surface of a packaging article and dried to form anoxygen scavenging coating. The coating dispersion may be applied betweenlayers of another suitable polymer to form an oxygen scavenging film.

Or, the oxygen scavenging polymer composition may be blended withanother compatible polymer to form an oxygen scavenging article, or maybe used as an oxygen scavenging layer in a multi-layered packageconstruction.

A broad variety of metallic and organic compounds can catalyze theoxygen scavenging effect of the side chains, and an appropriate compoundmay be selected based on any of cost, compatibility with the oxygenscavenging polymer, compatibility with other polymers in a blend, andcompatibility with other layers in a multi-layered package. Suitableoxidation catalysts include transition metals, complexes of transitionmetals, photoinitiators, and the like.

Examples of suitable catalysts include transition metals such as cobalt,iron, nickel, aluminum, ruthenium, rhodium, palladium, antimony, osmium,iridium, platinum, copper, manganese, and zinc, as well as oxides, saltsor complexes of these metals. For example, cobalt II salts of shortchain acids such as acetic acid or terephthalic acid, or long chainacids such as neodecanoic, stearic, 2-ethyl hexanoic, or octenylsuccinic acid may be used. Salts of inorganic acids may also be used.For example, antimony chloride III, antimony chloride V, and cobaltchloride may be used. Preferred catalysts include salts of cobalt andlong chain acids such as, for example, cobalt acetate, cobaltneodecanoate, cobalt stearate, and cobalt octoate.

Mixed metal nanoparticles may also be suitable as a catalyst. Suitablenanoparticles typically have an average particle size of less than about200 nm, preferably less than about 100 nm, and more preferably between 5and 50 nm.

Examples of suitable photoinitiators include, but are not limited to,benzophenone, o-methoxybenzophenone, acetophenone,o-methoxy-acetophenone, acenaphthenequinone, methyl ethyl ketone,valerophenone, hexanophenone, alpha-phenyl-butyrophenone,p-morpholinopropiophenone, dibenzosuberone, 4-morpholinobenzophenone,benzoin, benzoin methyl ether, 4-o-morpholinodeoxybenzoin,p-diacetylbenzene, 4-aminobenzophenone, 4′-methoxyacetophenone,alpha-tetralone, 9-acetylphenanthrene, 2-acetylphenanthrene,10-thioxanthenone, 3-acetylphenanthrene, 3-acetylindole, 9-fluorenone,1-indanone, 1,3,5-triacetylbenzene, thioxanthen-9-one, xanthene-9-one,7-H-benz[de]anthracen-7-one, benzoin tetrahydropyranyl ether,4,4′-bis(dimethylamino)-benzophenone, 1′-acetonaphthone,2′-acetonaphthone, acetonaphthone and 2,3-butanedione,benz[a]anthracene-7,12-dione, 2,2-dimethoxy-2-phenylacetophenone,alpha,alpha-diethoxyacetophenone, alpha,alpha-dibutoxyacetophenone, etc.Singlet oxygen generating photosensitizers such as Rose Bengal,methylene blue, and tetraphenyl porphine may also be employed asphotoinitiators. Polymeric initiators include poly(ethylene carbonmonoxide) andoligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone]. Blendsof photoinitiators may also be used.

Generally, photoinitiators must be activated to function mosteffectively. Photoinitiators may be activated using various types ofradiation. For example, the radiation used can be actinic, e.g.ultraviolet or visible light having a wavelength of about 200 to 750nanometers (nm), and preferably having a wavelength of about 200 to 400nm. When employing ultraviolet and/or visible light, it is preferable toexpose the composition to at least 0.1 Joules per gram of composition. Atypical amount of exposure is in the range of 10 to 100 Joules per gram.Another suitable type of radiation that can be used is an electron beam,having a suitable dosage from about 0.2 to about 20 megarads, preferablyfrom about 1 to about 10 megarads. Other possible types and sources ofradiation include ionizing radiation such as gamma, x-rays and coronadischarge. The radiation exposure is preferably conducted in thepresence of oxygen. The duration of exposure depends on several factorsincluding, but not limited to, the amount and type of photoinitiatorpresent, thickness of the layers to be exposed, amount and type of othercomponents present, and the wavelength and intensity of the radiationsource.

The oxidation catalyst should be present in an amount sufficient tocatalyze the oxygen scavenging ability of the oxygen scavenging polymer.The amount used will depend partially upon the catalyst chosen. However,in general, when using transition metal catalysts or complexes, theamount of transition metal catalyst or complexes present may suitably begreater than about 10 ppm by weight, preferably greater than about 100ppm by weight, and more preferably greater than about 300 ppm by weightof the total composition. The amount of transition metal catalyst orcomplexes present may suitably be less than about 10,000 ppm by weight,preferably less than about 1000 ppm by weight, and more preferably lessthan about 600 ppm by weight of the total composition. In general, whenusing a photoinitiator or blend of photoinitiators, the amount ofphotoinitiator present may suitably be greater than about 0.01% byweight, and preferably greater than about 0.1% by weight of the totalcomposition. The amount of photoinitiator present may suitably be lessthan about 10% by weight, and preferably less than about 5% by weight ofthe total composition.

In some embodiments, the method of introduction of the oxidationcatalyst may impact the resultant composition's performance orproperties. For example, in some cases the introduction of an oxidationcatalyst to the composition may cause undesirable side-reactions withinthe composition that can lessen the composition's molecular weight, orcause discoloration of the composition. Other factors which mayinfluence the composition's propensity to degrade include: the presenceof appreciable amounts of water during melt processing of the polymer;the presence of foreign reactive functionalities (such as hydroxyl,amino, thiol, carboxylic acid, etc.) during melt processing of thepolymer; the presence of appreciable amounts of molecular oxygen duringmelt processing of the polymer; and/or the presence of appreciableamounts of strongly acidic (e.g., HCl, H₂SO₄), or strongly basic (e.g.,KOH, etc.) materials during melt processing of the polymer. Care shouldbe taken to avoid such undesirable results, for example, by lesseningthe concentration of the aforementioned water, foreign reactivefunctionalities, molecular oxygen, or acidic or basic materials duringmelt processing of the polymer.

One consideration in this regard involves the choice of oxidationcatalyst. It has been discovered that certain oxidation catalysts areless prone to catalyzing the aforementioned undesirable side-reactions.As a result, one can, in some situations, select a suitable oxidationcatalyst (i.e., a catalyst that provides the desired level of oxygenscavenging) that does not cause an undesirable amount of degradation ofthe composition. For example, cobalt oxide can generally be introducedto the composition with little observable degradation.

Another consideration is the conditions under which the oxidationcatalyst is added to the composition. For example, it has been observedthat prolonged exposure at high temperature of certain compositionscontaining the oxidation catalyst will result in an increased amount ofdegradation. As a result, it has been discovered that processes thatavoid prolonged, high temperature exposure of the oxidation catalystwithin the composition can be beneficial. This can be done, for example,by lessening exposure of the molten polymer to excessive levels of shearduring mixing and/or transporting. Alternatively, the oxidation catalystcan be added to pre-formed polymer using mild melt mixing techniquessuch as a Buss kneader. Alternatively, the composition may be preparedin a batch reactor and the catalyst added quantitatively in a mannerthat minimizes the residence time of the molten polymer/catalyst blendprior to ejection, and cooling. In an extruder reactor the catalyst maybe added near the ejection port to minimize residence time of moltenpolymer with catalyst.

In the event some molecular weight degradation does occur, then it iswithin the scope of this invention to subject the degraded compositionto a solid-stating process to rebuild the molecular weight. For moreseriously degraded materials, the composition might need to be purifiedto remove or lessen the amount of undesirable discolored material.

Another aspect of the present invention is an article including anoxygen scavenging polymer or oxygen scavenging polymer composition.Articles, including but not limited to, bottles, cups, bowls,containers, films, wraps, liners, coatings, trays, cartons, and bags forindustrial, commercial, or residential use may be formed and produced.The articles may be formed by using the oxygen scavenging polymer and/orcomposition alone, by using a blend of the oxygen scavenging polymerand/or composition with one or more other polymers, or by using amulti-layer construction incorporating one or more layers including theoxygen scavenging polymer and/or composition. Additionally, the oxygenscavenging polymer and/or composition may be used as a coating, as alining, or as part of a blend for a coating or lining of anotherarticle, such as a can, bottle, or container coating or lining.

A single layer article is an article formed of substantially the samecomposition throughout. For example, the article may be produced usingonly the oxygen scavenging polymer and/or composition, or it may beproduced using a blend of the polymer and/or composition with one ormore other polymers. For example, a single layer bottle would typicallybe produced using a blend of up to about 10% of the oxygen scavengingpolymer composition and 90% of another polymer suitable for packagingapplications, such as PET, PEN, and the like.

Compatible polymers should be selected if a blend is prepared.Preferably, a polymer will be selected that has similar viscosity andsimilar characteristics to the oxygen scavenging polymer and/orcomposition. If a blend is used, the blend may be formed at any point,but preferably will be formed during the article production process. Theoxygen scavenging polymer and/or composition and a compatible polymermay be fed separately into the article production process, and thenblended during the process before being formed into the desired article.For example, the separate polymers may be fed into an injection molder,and the components will melt and blend in the screw of the injectionmolder. Then, the combination will jointly be formed into the producedarticle. The single layer article will scavenge oxygen passing throughthe material, oxygen within the container during filling or storage, aswell as oxygen at the outside surface.

For example, a polyester based polymer composition may be blended withanother polymer, having similar viscosities and other properties toenable a high degree of mixing and increase the consistency of the finalarticle. Examples of suitable polyester resins include, but are notlimited to, polyethylene terephthalate (PET), polybutylene terephthalate(PBT), polyethylene naphthalate (PEN), and polybutylene naphthalate(PBN). The appropriate polymer will be selected to provide the desiredfinal article properties. Additionally, factors such as blendcompatibility, resulting physical characteristics of the blend, andamount of the oxygen scavenging polymer composition included in theblend will be considered.

A multi-layer product may be produced that includes the oxygenscavenging polymer and/or composition. A multi-layer product benefitsfrom placing a layer of another material between the atmosphere and theoxygen scavenging polymer and/or composition. The outer layer willusually protect the oxygen scavenging polymer and/or composition fromphysical damage, and also assists in blocking some atmosphere and oxygenout. The oxygen scavenging polymer and/or composition will thereforeprimarily scavenge oxygen that penetrates the outer layer, or is presentinside the container during filling or storage. Therefore, an additionaloutside layer may be beneficial in extending the effectiveness of thearticle, while maintaining other desirable properties. An additionaloutside layer may also enable the same effective oxygen protection whileusing less of the oxygen scavenging polymer and/or composition. Aparticularly preferred multi-layer product is a five layer bottle inwhich the outer, central, and inner layers were formed using PET. Theouter-central and the inner-central layers were formed using the oxygenscavenging polymer.

The compatibility of the materials used is an important considerationfor a multi-layer article. If the materials are not compatible, thelayers may separate or the material may appear cloudy or hazy. Layerseparation could lead to failure of the article, decrease clarity evenfurther, degrade the strength or resilience of the article, change thefunctionality, and might lead to premature exhaustion of the oxygenscavenging polymer composition. Appropriate adhesives or other materialsmay be required for use between layers to maintain article integrity,which may lead to increased costs, manufacturing challenges, and mayimpact recycling. Therefore, the layers will preferably be compatible ifa multi-layer article is produced. For example, polymers having similarphysical properties such as a viscosity and Tg may be used inconjunction with the oxygen scavenging polymer and/or composition.

An oxygen scavenging polymer may be formed using a wide range ofprocesses, including, for example, reactor polymerization and reactiveextrusion.

Reactor polymerization includes batch and continuous processing. Variouscomponents may be charged into a reactor, and the reaction conditionsset. After suitable reaction time, the composition may be removed.

In reactive extrusion, the components may be fed into the mixing zone ofthe extruder. The components may be mixed together before feeding in tothe extruder, or may be fed separately. Preferably, the components willbe fed separately. As part of the extrusion process, the components willbe subjected to elevated temperature, pressure, and shear as thecomponents travel through the extruder. This process mixes thecomponents, and also causes the components to react, forming the polymercomposition.

For example, a preferred method of forming the oxygen scavenging polymeris to react one or more polymer precursors (monomers), a succinicanhydride derivative, and a polymerization catalyst. The polymerprecursors will be monomers that will polymerize with other monomers andthe succinic anhydride derivative to form the desired polymercomposition.

For example, a polyester may be formed using a glycol and a succinicanhydride derivative. Other polyesters may be formed using a polymerprecursors selected from a number of dicarboxylic acid components.Suitable examples of dicarboxylic acid components include, but are notlimited to, terephthalic acid, isophthalic acid, naphthalic acid,2,6-naphthalene dicarboxylic acid, other naphthalene dicarboxylic acidisomers, mixtures of dicarboxylic acid components, and derivativesthereof. The dicarboxylic acid components may be present as derivatives,such as, for example, bis-hydroxyethyl terephthalate. Similarly, othersuitable components may be selected and used in forming other types ofpolymers such as polyamide, polyepoxy, and polyurethane polymers.

Alternatively, the components used may include one or more polymers, asuccinic anhydride derivative, and a polymerization catalyst. Thepolymer will react with the succinic anhydride derivative to form thedesired polymer composition. This is the preferred method when usingreactive extrusion, but may also be accomplished using a reactor.Suitable polymers for use in this process include polyesters such asPET, PBT, PEN, and PBN. Similarly, other suitable polymers will be usedwhen forming a polyepoxy, polyamide, or polyurethane. Additionally, newor recycled resins may be used.

Examples of suitable succinic anhydride derivatives include a reactionproduct of maleic anhydride and a substituted alkene. Suitablesubstitutents for the alkene include saturated or unsaturatedhydrocarbon chains that may be linear or branched, and substituted orunsubstituted, as well as substituted or unsubstituted phenyl groups.Some of the substituents on the alkenyl group may be bound together aspart of a ring structure. Preferred succinic anhydride derivativesinclude octenyl succinic anhydride (OSA), nonenyl succinic anhydride(NSA), heptenyl succinic anhydride (HSA), and the like. Octenyl succinicanhydride (OSA), shown in Formula (II), is particularly preferred.

The benefits of using a succinic anhydride derivative include: ease ofprocessing; general availability at low cost; ability to co-polymerize;compatibility with many polymers and monomers for reaction; stabilityduring storage; and low toxicity.

The succinic anhydride may be reacted with a wide variety of materials,depending upon the type of polymer backbone desired. For example,reactants may be selected to form a succinic anhydride derivative, whichmay then react to form the desired side chain monomer. For example, if asuccinic anhydride derivative is reacted with an alcohol or glycol, theresulting compound can be used to form a polyester. As another example,a succinic anhydride derivative may be reacted with an amine, and thenused in a polymerization, forming a polyamide.

When using a reactor, a succinic anhydride derivative may be formedprior to addition to the reactor, or may be formed from a succinicanhydride and another component in the reactor. When using reactiveextrusion, a succinic anhydride derivative will preferably be used.

The materials used may also add other, additional features to theresulting polymer. For example, a trifunctional polyol could be used toform the succinic anhydride derivative, which would lead to additionalbranching in the resulting polymer.

A polymerization catalyst is preferably used to promote thepolymerization reaction. Suitable polymerization catalysts includetransition metal catalysts such as manganese, iron, antimony, ortitanium. The transition metal catalyst should be added in an amountsufficient to catalyze the polyester reaction. The amount ofpolymerization catalyst present may suitably be greater than about 10ppm by weight, preferably greater than about 100 ppm by weight, and morepreferably greater than about 200 ppm by weight, based on the totalweight of the reaction mixture. The amount of polymerization catalystpresent may suitably be less than about 1000 ppm by weight, preferablyless than about 800 ppm by weight, and more preferably less than about500 ppm by weight.

In addition, a compound, such as, for example, phosphoric acid may beused to deactivate any transesterification catalyst (e.g., manganesetransesterification catalyst) that may be present.

A wide variety of additional components may be present in the polymercomposition of the present invention without detracting from its oxygenscavenging properties, and this is particularly important when recycledresins, such as recycled polyesters, are used.

Depending on the intended end use of the packaging material, optionaladditives may be incorporated into the oxygen scavenging polymercomposition. Suitable additives include heat stabilizers, antioxidants,colorants, crystallization agents, blowing agents, fillers, accelerants,and the like. Preferably, an anti-oxidant, such as BHT, will be added,as the anti-oxidant enhances the stability of the oxygen scavengingcomposition during processing.

Whether the oxygen scavenging polymer is formed using reactorpolymerization, reactive extrusion, or other method, an oxidationcatalyst can be added at different times, forming the oxygen scavengingpolymer composition. Suitable locations for addition of an oxidationcatalyst include: adding the catalyst into the reactor duringpolymerization, adding the catalyst into an extruder during reactiveextrusion, adding the catalyst as the polymer is formed into pellets, oradding the catalyst together with the polymer composition during thearticle production process. For example, pellets of the oxygenscavenging polymer may be blended with pellets of another polymer havingthe oxidation catalyst therein. The blend of these pellets may then becombined (e.g., melted and mixed), during or immediately precedingarticle fabrication.

In addition, whether the oxygen scavenging polymer is formed usingreactor polymerization, reactive extrusion, or other method, theresulting polymer composition can be used in forming articles, may bestored, or may be sent for further processing. Possible furtherprocessing steps include pelletization and solid stating.

After the oxygen scavenging polymer is formed, it may be processed forease in handling, storage, and later use. One method to accomplish thisis pelletization, in which a polymer composition is chopped or groundinto small pieces or flakes. Other components may also be added duringthis process.

As a polymer composition forms, it also increases in molecular weight.The reaction process also leads to increasing viscosity of the material.As a polymer composition becomes more viscous, it also becomes moredifficult to process. Therefore, solid stating is often used in polymerformation. Solid stating refers to a process in which a polymer isformed, and when the polymerization reaches a certain point (or acertain viscosity is reached) the polymerization is temporarily stopped.At this point, polymer pellets are formed, as the polymer is still ableto be handled and processed relatively easily. The polymer pellets arethen fed into a rotary vacuum dryer (available from Stokes Vacuum Inc.).The rotary vacuum dryer incorporates temperature control for heating,and has a tumbler to keep the pellets loose and free flowing. Thepellets are introduced, tumbling is begun, and heat is introduced. Thiscauses the polymerization reaction to continue within the pellets. Thiscontinued reaction forms higher molecular weight polymers, which aremore useful than polymers of lower molecular weight in manyapplications. Because the polymerization continues and molecular weightincreases within the pellets, handling and processing remains the same.Solid stating may be used in conjunction with any of the methods usedfor forming the polymer composition.

For example, when creating a polyester, it may be desirable to selectcomponents to provide a composition with a melt viscosity as close aspossible to about 0.8 intrinsic viscosity. This provides excellentcompatibility with bottle grade PET, which has an intrinsic viscosity ofabout 0.80 to about 0.85. Thus, a polyester may be formed by: (1)reacting until a certain viscosity is reached; and then optionallyperforming the following techniques, either alone or in combination: (2)solid stating; and/or (3) introducing branching into the polymer usingmaterials such as, for example, pyromellitic dianhydride (PMDA) toincrease melt viscosity (See, for example, U.S. Pat. No. 6,863,988).This would form an oxygen scavenging polymer composition having thedesired viscosity and the desired molecular weight.

Appropriate care must be used when handling and storing the oxygenscavenging polymer, particularly after the oxidation catalyst has beenadded to form the oxygen scavenging composition. Specifically, exposureto oxygen should be minimized until use. Therefore, production andstorage of the composition under conditions eliminating or minimizingoxygen are preferred. For example, the composition may be stored inwell-sealed containers, or under an inert atmosphere such as nitrogen,until use.

Tests of an oxygen scavenging polymer composition may be conducted byvarious methods. Oxygen content of a gas sample may be analyzed by theOcean Optics Foxy Oxygen Sensor System (available from Ocean Optics,Dunedin, Fla.). This system uses fluorescence and quenching to measureoxygen content.

In order to test the viscosity of the oxygen scavenging polymer, variousviscosity tests may be employed. One testing scheme, solution viscosity,is carried out via dissolving an amount of the oxygen scavenging polymercomposition in an appropriate solvent. Another testing scheme is meltviscosity, using a Dynisco or other capillary rheometer may be used.This test is conducted following ASTM D3835-96 “Standard Test Method forDetermination of Properties of Polymeric Materials by Means of aCapillary Rheometer.” This test is conducted by testing the viscosity ofthe composition in a liquid form. Preferably, a melt viscosity test willbe used, as the viscosity that is important is the viscosity of thematerial during manufacturing, or the viscosity in the molten state.

EXAMPLES Example 1

An oxygen scavenging polymer was produced using the following procedure:

A vacuum vessel equipped with high torque agitation, temperaturecontrol, vacuum, and a Nitrogen purge was prepared. The prepared vesselis capable of achieving a vacuum of less than 1 torr, and is able toreach a temperature of 285° C. or higher.

The set point on the reactor heating is set to 285° C. When the reactortemperature reaches 185° C., sufficient Nitrogen is purged through thesystem to eliminate Oxygen. After purging, 2242 grams of Bis-HydroxethylTerephthalate (BHT), a fine flowing powder, 558 grams ofBis-Hydroxyethyl Octenylsuccinate, a viscous liquid, 0.57 grams ofTitanium catalyst (Tyzor TOT), and 0.14 grams of Sb₂O₃ are charged intothe reactor with agitation. The system is closed, agitation continues,and vacuum is slowly applied. During polymerization, ethylene glycol isgiven off by the reaction of the components, and is removed by boilingoff under vacuum. When the desired agitator torque has been achieved,the reactor is vented with Nitrogen to atmospheric pressure and thematerial is discharged.

Example 2

The same reaction conditions as described in Example A were established.Then, the following components charged to the reactor: 27.230 kg ofdimethylterephthalate (DMT); 5.895 kg of octenyl succinic anhydride(OSA); 20.880 kg of ethylene glycol, 16.7 grams of manganese(II) acetatetetrahydrate; 7.1 grams of phosphoric acid; and 24.5 grams of antimony(III) oxide.

The same reaction conditions were followed, except that, in this case,water and methanol were given off during the esterification step of thereaction. Thus, the water and methanol by-products were removed undervacuum. Additionally, there was a small amount of glycols that were alsoremoved by vacuum.

Example 3

Another oxygen scavenging polymer was produced using the followingprocedure:

A flask equipped with agitation, temperature control, reflux condensorwith provisions for collecting distillate, and a Nitrogen purge wasprepared. The flask was charged with 1556.7 g of OctenylsuccinicAnhydride and 942.0 grams of Ethylene Glycol. A Nitrogen flow was alsoestablished. Under continuous agitation, the contents of the flask wereheated to a setpoint of 170° C. After the onset of water distillation,1.25 grams of Fascat 4201 catalyst was charged into the flask, and thetemperature setpoint was raised to 200° C. After 91.4 grams distillatewere collected, the temperature setpoint was raised to 210° C. After118.9 grams distillate were collected, the setpoint was raised to 220°C. The reaction was ended when the product reached an Acid Number of0.6.

Example 4

Yet another oxygen scavenging polymer was produced using the followingprocedure:

A flask equipped with agitation, temperature control, reflux condensorwith provisions for collecting distillate, and a Nitrogen purge wasprepared. The flask was charged with 345.0 g of C16-C18 Alkenyl SuccinicAnhydride, 62.0 grams of Ethylene Glycol, and 0.34 g of DibutyltinOxide. A Nitrogen flow was also established. Under continuous agitation,the contents of the flask were heated to a setpoint of 200° C. Thereaction was ended when the product reached an Acid Number of 24.

Example 5

Another oxygen scavenging polymer was produced using the followingprocedure:

A flask equipped with agitation, temperature control, reflux condensorwith provisions for collecting distillate, and a Nitrogen purge wasprepared. The flask was charged with 304.0 g of TetrahydrophthalicAnhydride, 124.0 grams of Ethylene Glycol, and 0.40 g of DibutyltinOxide. A Nitrogen flow was also established. Under continuous agitation,the contents of the flask were heated to a setpoint of 230° C. Thereaction was ended when the product reached an Acid Number of 5.6.

Example 6

A sample prepared according to Example 3 was mixed with 5% w/w of aCobalt catalyst (OMG 12% Cobalt Hex-Cem) to form an oxygen scavengingcomposition. Two test samples were prepared by coating 30-35 mg of thismixture onto a glass plate.

A sample prepared according to Example 4 was mixed with 5% w/w of aCobalt catalyst (OMG 12% Cobalt Hex-Cem). Two test samples were preparedby coating 120 mg of this mixture onto a glass plate.

A sample prepared according to Example 5 was mixed with 5% w/w of acobalt catalyst (OMG 12% Cobalt Hex-Cem). Two test samples were preparedby coating 30-35 mg of this mixture onto a glass plate.

Two samples of steel wool were prepared by wetting the steel wool. Inaddition, samples of a PET monolayer bottle were prepared for use as acontrol.

All test samples were individually sealed inside 15.24 cm×7.62 cm(6″×3″) heat sealable foil pouches. The bags were heat sealed under 1atmosphere of pressure, which has an oxygen content of 20.948%. Sampleswere stored at ambient temperature and at 49° C. (120° F.) in a hotroom. After one week, air samples were taken from the sealed pouches andanalyzed using an Ocean Optics Foxy Oxygen Sensor System. The resultswere measured after two minutes of exposure to the sensor. The oxygenscavenging effectiveness of the material was calculated by subtractingthe oxygen content measured after 1 week from the initial oxygen contentand dividing by the weight of the sample material used. The results arereported in Table 1.

TABLE 1 % Oxygen Scavenged/mg % Oxygen Scavenged/mg Scavenger (RoomScavenger Sample Temperature) (49° C. (120° F.)) Control #1 0.00 0.00Control #2 0.00 0.00 Wet Steel 0.07 0.07 Wool #1 Wet Steel 0.07 0.07Wool #2 Example 3 #1 2.07 3.18 Example 3 #2 2.61 3.03 Example 4 #1 1.472.34 Example 4 #2 0.45 2.88 Example 5 #1 0.06 0.18 Example 5 #2 0.060.18

Example 7

A sample prepared according to Example 1 was fed into a Brabenderextruder in conjunction with polyethylene terephthalate. A cobaltcatalyst (OMG 12% Cobalt Hex-Cem) was also fed into the extruder at thesame time to provide the resulting compositions with 5% w/w Cobaltcatalyst. The feed conditions were modified to create two compositions,one composition having 10% w/w of the material from Example 1, and onecomposition having 20% w/w of the material from Example 1. Films wereextruded having thickness of 12 microns and 24 microns for bothcompositions. Each film were sealed inside 15.24 cm×7.62 cm (6″×3″) heatsealable foil pouches. The bags were heat sealed under 1 atm ofpressure, which has an oxygen content of 20.948%. After one week ofstorage at ambient temperature, air samples were taken from the sealedpouches and analyzed using an Ocean Optics Foxy Oxygen Sensor System.The % oxygen consumption was calculated for each sample, and the resultsare reported on Table 2.

TABLE 2 % Material from % Oxygen Example 1 Film Thickness (μ)Consumption 10% 12 97.8 ± 0.7   10% 24 96 ± 1.2 20% 12  27.3 ± 8.2** 20%24 80 ± 8.5 **= anomalous result likely caused by dense packing of filmin pouch, resulting in less exposed surface area

Example 8 Articles

A three layer bottle was produced, including outer and inner layers ofPET, and a central layer is formed using the oxygen scavenging polymersof examples 1 and 2 with a cobalt catalyst complex. The three layers hada high degree of compatibility, and tightly molded together during theproduction of the bottle.

A three layer film was produced in which the top and bottom layer areformed using PET, and the central layer was formed using the oxygenscavenging polymers of examples 1 and 2 with a cobalt catalyst complex.

A coating solution was formed by mixing 50% solvent and 50% of thepolymer composition of Example 3. A can coating was formed by sprayingthe coating dispersion on an inside surface of a metal can.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

1. A composition comprising: an oxygen-scavenging polymer that includesa condensation backbone having at least one structural unit representedby formula (I):

wherein R₁, R₂, R₃, R₄, and R₅ independently denote one of a hydrogenatom, a substituted or unsubstituted alkyl group, a substituted orunsubstituted cycloalkyl group, or a substituted or unsubstitutedalkenyl group, and n denotes an integer from 1 to 10; and at least about10 parts per million (ppm) by weight of an oxidation catalyst.
 2. Thecomposition of claim 1, wherein R₁ denotes hydrogen.
 3. The compositionof claim 1, wherein R₁, R₂, R₃, R₄, and R₅ each have less than 20 carbonatoms.
 4. The composition of claim 1, wherein R₄ and R₅ denote hydrogen.5. The composition of claim 1, wherein R₁, R₂, and R₃ each comprise lessthan 10 carbon atoms.
 6. The composition of claim 1, wherein n is aninteger less than
 5. 7. The composition of claim 1, wherein R₁, R₃, R₄,and R₅ each denote hydrogen, wherein n=1, and wherein R₂ denotes alinear substituted or unsubstituted alkyl group with 1 to 10 carbonatoms.
 8. The composition of claim 7, wherein R₂ denotes a linear alkylgroup with 5 carbon atoms.
 9. The composition of claim 1, wherein thebackbone is a polyester.
 10. The composition of claim 1, wherein between1 and 30 weight percent of the polymer comprises monomers including thestructural unit.
 11. The composition of claim 1, wherein between 2 and25 weight percent of the polymer comprises monomers including thestructural unit.
 12. The composition of claim 1, wherein between 10 and20 weight percent of the polymer comprises monomers including thestructural unit.
 13. The composition of claim 1, wherein the catalyst ispresent at a concentration from about 10 ppm to about 1000 ppm byweight.
 14. The composition of claim 1, wherein the catalyst is presentat a concentration from about 300 ppm to about 600 ppm by weight. 15.The composition of claim 1, wherein the catalyst comprises one or moretransition metal complexes.
 16. The composition of claim 1, wherein thecatalyst comprises the reaction product of cobalt and a long chain acid.17. The composition of claim 1, wherein the catalyst is selected fromthe group consisting of cobalt neodecanoate, cobalt stearate, and cobaltoctoate.
 18. The composition of claim 1, wherein the catalyst comprisesa uv-activated catalyst.
 19. The composition of claim 1, furthercomprising a filler, colorant, antioxidant, heat stabilizer,crystallization agent, blowing agent, or accelerant.
 20. A solutioncomprising the composition of claim 1 and a solvent.
 21. An articlecomprising the composition of claim
 1. 22. An article comprising a layerof the composition of claim
 1. 23. The article of claim 22, furthercomprising a second layer of a second polymer.
 24. The article of claim23, wherein the second polymer is polyethylene terephthalate.
 25. Thecomposition of claim 1, wherein the condensation backbone comprises apolyurethane.
 26. The composition of claim 1, wherein the condensationbackbone comprises a polyepoxide.
 27. The composition of claim 1,wherein the condensation backbone comprises a polyamide.
 28. The articleof claim 22, wherein the article comprises a packaging article.
 29. Thearticle of claim 28, wherein the article comprises a bottle.
 30. Apackaging article, comprising: a layer of an oxygen-scavengingcomposition including: an oxygen-scavenging polymer comprising acondensation backbone having at least one pendant group represented byformula (I) attached to a carbon atom of the backbone:

wherein, R₁, R₂, R₃, R₄, and R₅ independently denote one of a hydrogenatom, a substituted or unsubstituted alkyl group, a substituted orunsubstituted cycloalkyl group, or a substituted or unsubstitutedalkenyl group, and n denotes an integer from 1 to 10; and at least about10 parts per million (ppm) by weight of an oxidation catalyst.